Untangling Multiple Strands of Hype, Stupidity And Complexity In The Great Tree-Planting Panacaea

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Last year, the World Economic Forum (WEF) launched its 1t.org project, which aims to mobilize commitments from corporations, governments, and NGOs to “conserve, restore, or grow” one trillion trees by 2030. One of its leading supporters is Marc Benioff, the billionaire CEO of Salesforce, who pledged funds to plant 100 million of them. During the 2020 WEF meeting in Davos, Switzerland, Benioff announced that 300 companies and numerous governments have committed to hitting 1t.org’s target. And their numbers keep growing: A company called tentree recently promised to plant a billion trees by 2030, beating Benioff’s commitment by an order of magnitude. “Nobody’s against trees,” said Benioff, adding, “This is a time of action, not words. We are at that point of urgency with our planet.” But a growing number of scientists and environmentalists are challenging this narrative on tree-planting. They say that planting programs, especially those based on large numerical targets, can wreck natural ecosystems, dry up water supplies, damage agriculture, push people off their land — and even make global warming worse. They point to flaws in the studies that have inspired large-scale programs, and say that harmful types of tree planting are regularly conflated with beneficial natural forest restoration. Tree planting can distract from the greater priorities of protecting existing forests and reducing fossil fuel use, they say, and conserving and restoring natural open ecosystems, like grasslands, can often deliver more benefits than afforestation.

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In South Africa, for example, many naturally open habitats, including grasslands and heathlands, have been invaded by introduced trees like eucalyptus and acacia species from Australia and pines from the Northern Hemisphere. Research shows that these non-native trees can consume significantly more water than native plants and can dry up rivers and wetlands. They also crowd out native species and increase the fuel available to wildfires, making these more dangerous. South Africa has recently faced critical water shortages affecting major cities that have been exacerbated by invasive trees, and the government spends millions of dollars annually on a program called Working for Water to remove them from key watersheds and conservation areas.

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Because of climate change, forests are increasingly vulnerable to destruction by drought, fire, insects, diseases, and storms, which releases carbon back into the atmosphere. Recent research shows that large areas of the American West may have permanently lost their forest cover. Droughts, wildfire, and insect and disease outbreaks are becoming more frequent, and forests are being replaced by grassy shrublands after these disturbances, mostly because it’s now too hot and dry for new generations of saplings to survive. A review paper published in Science last year shows that these threats, although significant and intensifying, aren’t always well understood and are difficult to compensate for. It’s hard to predict how many trees they’ll kill in the near future and how much carbon that will put into the atmosphere, but it’s likely to be considerable.

Not only might tree planting fail to reliably sequester carbon, trees can also heat the atmosphere more than many other habitat types. Kathleen Smart, a post-doctoral researcher at Rhodes University in South Africa, says that replacing surfaces like grasslands or deserts —which, being pale, reflect more solar radiation into outer space — with relatively dark-colored tree plantations can have a heating effect on a local level, and that regional-scale land-use changes have been shown to affect climate and rainfall patterns. Although it would take an enormous area of new trees to measurably heat the atmosphere at a global scale, Smart says in some cases the planetary reflectance loss from new trees may outweigh carbon sequestration gains.

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https://e360.yale.edu/features/are-huge-tree-planting-projects-more-hype-than-solution

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